Immunogenicity, Safety, and Efficacy of Abatacept Administered Subcutaneously With or Without Background Methotrexate in Patients With Rheumatoid Arthritis: Results From a Phase III, International, Multicenter, Parallel‐Arm, Open‐Label Study

Abstract

To evaluate the impact of concomitant methotrexate (MTX) on subcutaneous (SC) abatacept immunogenicity, and to assess safety and efficacy. This phase III, open-label study had a 4-month short-term (ST) period and an ongoing long-term extension (LTE) period. Rheumatoid arthritis patients were stratified to receive SC abatacept (125 mg/week) with (combination) or without MTX (monotherapy), with no intravenous loading dose; patients receiving monotherapy could add MTX in the LTE period. Immunogenicity (percentage of anti-abatacept antibody-positive patients) was assessed. ST and LTE period data are reported, including efficacy through LTE month 14 and safety through LTE month 20. Ninety-six of 100 enrolled patients completed the ST period; 3.9% (combination) and 4.1% of patients (monotherapy) developed transient immunogenicity, and no patients were antibody positive at month 4. Serious adverse events (SAEs) were reported in 3.9% (combination) and 6.1% of patients (monotherapy); 5.9% (combination) and 8.2% of patients (monotherapy) experienced SC injection reactions, and all were mild in intensity. Mean 28-joint Disease Activity Score (DAS28) changes were -1.67 (95% confidence interval [95% CI] -2.06, -1.28; combination) and -1.94 (95% CI -2.46, -1.42; monotherapy) at month 4. Ninety patients entered and were treated in the LTE period; 83.3% (75 of 90) remained ongoing at month 24. One LTE-treated patient (1.1%) developed immunogenicity, 14.4% of patients experienced SAEs, and no SC injection reactions were reported. For patients entering the LTE period, mean DAS28 changes from baseline were -1.84 (95% CI -2.23, -1.34; combination) and -2.86 (95% CI -3.46, -2.27; monotherapy) at month 18. SC abatacept did not elicit immunogenicity associated with loss of safety or efficacy, either with or without MTX.